DE 100 39 381 A1 discloses a drive system for a floor conveyance, in particular a lifting trolley, which comprises two essentially co-axial wheels with a transmission arranged at least partially between them. The wheels can be driven by an electric, traction motor, here called the drive motor, via the interposed transmission. In addition, an electric, steering drive can be provided. The transmission housing, together with the wheels, are attached to a chassis of the floor conveyance and able to swivel about a substantially vertical axis.
From DE 103 28 651 A1 a comparable arrangement concerning a drive system for a floor conveyance is known, whose structure is intended to be particularly space-saving. Accordingly, the drive motor is connected with a steering motor co-axially adjacent to and underneath it, which is attached to a chassis component of the floor conveyance. An outer bushing of a bearing arrangement is bolted to the chassis component, co-axial with the drive motor, and thus also with the steering motor. An inner bushing of the bearing arrangement is connected to a housing cover of a drive transmission, which serves as a center pivot plate. On the center pivot plate or housing of the drive transmission is mounted at least one rotating wheel, which can be driven by the drive motor with the drive transmission interposed.
The electric drives of known floor conveyances mainly consist of a three-phase motor with an associated electric transverter and corresponding control electronics. It is obvious to those familiar with the subject that the operation of such drive systems and the efforts to make them compact results in increased development of heat.
To avoid heat concentration and overheating of the motors, the transverter and/or other electrical or electronic components, conventionally the system is cooled by convection or, as indicated in more detail in DE 102 41 420 A1, by way of a fan-wheel arranged on the motor shaft. It is evidently insufficient when a very compact structure of the drive system allows only limited free space for the cooling airflow.
Against that background the purpose of the invention is to provide an electric drive system for floor conveyances, with improved cooling performance.